Purpose: The Epidemiology and Biostatistics Core will provide a wide range of consultative services to Center Members to facilitate the design, collection and analysis of nutrition, endocrine, and metabolic (NEM)-related data among injection drug users (IDUs) from the collaborating sites. These services will include: 1) consultations on study design, analytic methods, and database and questionnaire design: 2) performance of power/sample size calculations for new studies and grants resulting from Center-related activities; 3) design and management of centralized databases for multi-site, Center-wide studies: and 4) development of standardized NEM-related data collection instruments and protocols to be used by Center-supported projects. The Epidemiology and Biostatistics Core will play a major role in the design and implementation of the initial multi-site, Center-wide study. The Core will also play a key role in the design and implementation of new grants and studies that will be generated by the Center.